Coal mine gases sensors with dual selectivity at variable temperatures based on a W18O49 ultra-fine nanowires/Pd@Au bimetallic nanoparticles composite

In spite of protecting the safety of miners has been valued by departments, it is still a severe technical challenge to monitor coal mine gases which are generally explosive or poisonous. In this work, Pd@Au core-shell bimetallic nanoparticles (BNPs) are employed to decorate ultra-fine W18O49 nanowires (NWs), which are consequently used to detect coal mine gases. The W18O49 NWs were synthesized by a facile solvothermal method. And different noble metals including Pd and different BNPs were prepared for constructing metal oxide semiconducting gas sensors (MOS). Their structures and morphologies were characterized in detail, and the gas sensing mechanism was discussed in depth. It has been found that W18O49 NWs decorated with Pd@Au BNPs own enhanced gas sensing properties toward H2S and CH4. More importantly, W18O49 NWs/BNPs-2 has dual selectivity at different temperatures. At 100 ℃, the response of the optimized sensor to 50 ppm H2S is 55.5, accordingly, it has only little response to CH4. While at 320 ℃, the response to 1000 ppm CH4 is 7.8, and exhibits good selectivity. This work is of significance for the detection of coal mine gases, and has an application potential in ensuring the safety of mine work. •The ultra-fine one dimensional W18O49 nanowires (less than 1 nm in diameter) can provide more adsorption sites and transport channels, and a large number of oxygen defects play a crucial role in improving the gas sensing performance.•The decoration of Pd@Au core-shell Bimetallic Nanoparticles can form Schottky barrier at the contact interface on the W18O49 NWs, which thicken the thickness of the sensing layer and makes its resistance change greatly, thus improving the gas sensing performance.•In this work, we achieved dual sensitivity and selectivity at different temperatures. At low temperature, the response of the optimized sensor W18O49 NWs/BNPs-2 to H2S is high, but the response to CH4 is very low, which is due to the high symmetry of CH4 molecule; when the temperature increases, the response to CH4 increases.